The present invention relates to electric connectors and, more particularly, to a tin paste overflow-protective electric connector, which prevents a short circuit during its installation in a circuit board.
When fastening an electronic device, for example, an electric connector to a circuit board, the terminals of the electronic device are inserted through respective through holes and then fixedly soldered to the respective through holes of the circuit board. Alternatively SMT (surface mounting technology) may be employed to bond the terminals of the electronic device to the tin paste at the respective pads of the circuit board. For mass production, SMT is commonly used to install electronic devices in circuit boards at two sides. During the application of SMT, an electrically conductive medium, for example, tin paste is applied to the circuit board, and then electronic devices are attached to the circuit board, and then the circuit board with the electronic devices are put in a high temperature stove for baking, causing the electrically conductive medium to be melted and bonded to the respective mounting ends of the terminals of the electronic devices. After cooling, the terminals of the electronic devices are fixedly and electrically connected to the tin paste at the respective pads (contacts) of the circuit board. Because the terminals of the electronic devices are to be fastened to the respective pads of the circuit board, the electrically insulative shell of each electronic device has terminal holes through which the respective terminals extend to the outside for mounting. During baking in the high temperature stove, a siphon effect may be produced in the terminal holes, thereby causing the molten electrically conductive medium (the tin paste) to be sucked into the inside of the electrically insulative shell and covered over the contact end of each terminal. When an overflow of electrically conductive medium (the tin paste) occurs, the terminals may be short-circuited, or the structural strength of the terminals may be weakened. Further, in order to minimize installation space, electronic devices and/or connectors may be installed in both the top and bottom sides of a circuit board. In this case, the electronic devices and/or connectors at the front side of the circuit board will be heated twice in the high temperature stove.
FIG. 7 shows electronic connectors installed in top and bottom sides of a circuit board C. As illustrated, each electric connector comprises an electrically insulative shell A, and a plurality of terminals B respectively fastened to respective terminal holes A1 in the electrically insulative shell A. Each terminal B has a contact end B1 suspended inside the electrically insulative shell A, and a mounting end B2 disposed outside the electrically insulative shell A for bonding to the tin paste C11 at the corresponding pad (contact) C1 of the circuit board C by SMT (surface mounting technology). During bonding of electronic connectors to the tin paste C11 at the pads C1 at the bottom side of the circuit board C after installation of respective electronic connectors in the top side of the circuit board C, the tin paste C11 at the mounting ends B2 of the terminals B of the electronic connectors at the top side of the circuit board C is melted again. At this time, the molten tin paste tends to be drawn into the inside of the electrically insulative shell A through the respective terminal holes A1, and covered over the contact ends B1 of the terminals B of the electronic connectors at the top side of the circuit board C, causing a short circuit.
FIG. 8 shows an electric connector fastened to respective through holes in a circuit board according to the prior art. As illustrated, the mounting ends B2 of the terminals B are extended out of respective terminal holes A1 of the electrically insulative shell A and inserted through respective tubular contacts C1 in the circuit board C, and then bonded to the tin paste C11 in the tubular contacts C1. Because the electronic connector has a small height (some electric connectors are shorter than 0.9 mm), there is limited spacing space between the terminal holes A1 and the tubular contacts C1 in the circuit board C. During baking, the molten tin paste may flow over the mounting ends B2 of the terminals B, causing a short circuit.
The present invention has been accomplished to provide an electric connector, which eliminates the aforesaid problems. It is the main object of the present invention to provide a tin paste overflow-protective electric connector, which protects against an overflow of tin paste during its mounting on a circuit board. It is another object of the present invention to provide a tin paste overflow-protective electric connector, which is suitable for fastening to a circuit board by SMT (surface mounting technology). To achieve these and other objects of the present invention, the tin pate overflow-protective electric connector comprises an electrically insulative shell and at least one terminal respectively fastened to a respective terminal hole in the electrically insulative shell. Each terminal has a mounting end extended out of the respective terminal hole for fastening to a circuit board, a contact end suspended inside the electrically insulative shell for the connection of a matching electric connector, and a tin paste accumulation hole disposed inside the electrically insulative shell adjacent to one end of the corresponding terminal hole and adapted to collect an overflow of tin paste during surface mounting of the electric connector on the circuit board. During the application of SMT, the overflow of tin paste is accumulated in the tin paste accumulation hole of each terminal, and stopped from flowing to the contact end of each terminal.